This metal detector is reasonably priced at under $20, but you get what you pay for. When I tested this on a known area with metal under the wood (my workbench has screws attaching face to top), the detector failed to detect a #10 screw just under the wood’s surface! This is totally unacceptable. My jointer, planer. or bandsaw blades are too expensive to chance on this unreliable detector.
A magnetic stud finder is much more reliable than this! Save your money for the Lumber Wizar...